This invention relates to a method of making 1,1'-sulfonyl-bis (3-nitro-5-trifluoromethyl) benzene by reacting 1,1'-thiobis[3-(trifluoro-methyl) benzene] with fuming nitric acid and fuming sulfuric acid at a temperature below 20.degree. C., followed by raising the temperature to about 30.degree. to about 80.degree. C.
In co-pending application filed of even date by Jeffrey S. Stults and Henry C. Lin, titled "Novel Bis-M-Benzotrifluoride Compounds," Ser. No. 394,990, now abandoned in favor of continuation in part application Ser. No. 594,479, filed Oct. 9, 1990, herein incorporated by reference, there is disclosed the compound 1,1'-sulfonylbis[3-bis-nitro-5-(trifluoromethyl) benzene] (SBB), and the compound 1,1-sulfonylbis[3-nitro-5-(trifluoromethyl) benzenamine], which is made by reducing SBB. That application discloses that SBB can be made by first reacting benzotrifluoride meta-chloride with sodium sulfide to prepare 1,1'-thiobis[3-(trifluoromethyl) benzene]. In the next step, the benzotrifluoride sulfide is oxidized to the sulfone using an oxidizing agent such as hydrogen peroxide in acetic acid. Finally, the sulfone is nitrated using a mixture of fuming nitric acid and fuming sulfuric acid. While SBB can be prepared in good yield using that three-step process, a simpler and more direct process would be desirable.